I doubt you will need them either!
But they fill the same gameplay purpose, incremental rewards to make it feel like a very long questline is going somewhere and is worth doing now rather than in patch 5.4
this is a great idea to me, it's a "legendary" weapon that anyone can get but only by completing the expansion in its entirety. aka something that feels legendary.
maybe people just got spoiled with herp derp let me make a rogue alt so i can farm normal ds for orange daggers but this is both accessible to everyone (you can get your stupid sigils and sha touched weps in lfr if you don't even raid ffs) yet legendary in scope.
i have a feeling sha touched weapons are making a reappearance in 5.4 Siege of Orgrimmar raid.
everything points towards garrosh harnassing the power of the sha too strenghten his soldiers. so far he failed, but he might succeed somewhere in 5.2 or 5.3
from that standpoint it isnt weird too encounter new sha touched weaponary
But wait! Don't get out your pitchfork!
The reason isn't "to make it easier for newbs" but because you have to do the whole questline anyway.
Blizzard have already confirmed that for the 5.2 questline you will have had to finish the 5.0 and 5.1 questline.
They are already making sure that you have to play through the whole expansion's worth of raids to get the final reward. That doesn't require hanging on to your Sha-Touched weapon, the "quest completed" flag is proof enough.
Old gear gets replaced by new gear. More at 11.
The great world tree, Yggdrasil. Trembles, to it's roots.
I think that in the first part of the qline, Wrathion is just testing you.
Practically he shouldn't know you if you aren't a rogue.
His first 5.2 quest says that he needs a champion.
---------- Post added 2013-02-09 at 09:48 AM ----------
It's a convenience thing above all.